<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>一元运算符</title>
</head>
<body>
        <script>
            var a = 20;
            var b=a++;
           // a = 21;
           // b = 20;
            console.log(a);
            console.log(b)

        </script>
</body>
</html>